The mammalian retina is one of the richest sources of zinc (per weight of tissue) in the body. The trace metal probably subserves a variety of functions, one being an essential component for the activity of alcohol dehydrogenase. Other zinc-dependent reactions and processes have not been investigated systematically. We observed that chelators of divalent cations, when administered systemically, cause deposition of an electron-opaque material in the retina. The inclusion bodies are distinct from normal subcellular organelles such as lysosomes. Doses of chelator which affect the retina also cause significant reductions in serum zinc, and marginal reductions in blood glucose. Acute metal chelation does not affect ERG's in the rat, however maximal photocurrent was considerably larger after chelator injections. The retinae of zinc deficient rats display morphological alterations similar to rats given chronic and acute doses of trace metal chelators.